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Why Hair Turns Gray: Immune System Could Be To Blame

What is the science behind our hair turning gray? Researchers from the University of Alabama at Birmingham have a possible answer and it may also explain why vitiligo patients develop unpigmented patches of skin.

The study titled "A direct link between MITF, innate immunity, and hair graying" was published in the journal PLOS Biology on May 3.

"My lab harnesses the power of mouse models of hair graying to better understand stem cells and aging. The stem cells we study are the melanocyte stem cells in the hair follicle, which are the stem cells that are essential for producing melanocytes," explained lead study author Melissa Harris, an assistant professor of biology at the University of Alabama.

Melanocytes are pigment-producing cells responsible for giving your hair its natural color, be it blonde, brown, red or black. But when melanocytes suffer damage as a response to natural aging or a serious illness, the newly grown hair ceases to carry its natural pigment. This is how people develop gray or white hair.

Previously, the research team had found that a protein called MITF (melanogenesis-associated transcription factor) controlled the genes to create hair color pigment. The team examined mice that were bred to develop premature gray hair and found an excessive production of MITF. However, even when they bred mice to produce the protein at lower levels, their fur continued to turn prematurely gray at a similar pace as before.

The new research found that MITF may actually turn off genes for an anti-virus, immune protein called interferon. When the researchers triggered an anti-virus response in the mice, it was found that the mice having low levels of this protein ended up losing melanocytes and developing gray fur.

Since this was a mouse study, it remained unclear how far this mechanism could work in the case of human beings. But Harris pointed that it may be one of the possible reasons why some people suddenly develop gray hair in their youth. "Perhaps, in an individual who is healthy yet predisposed for gray hair, getting an everyday viral infection is just enough to cause the decline of their melanocytes and melanocyte stem cells leading to premature gray hair," she said.

Another significant takeaway from this discovered mechanism is that it may also explain disruptions in skin pigmentation in addition to affecting hair pigmentation.

"These results may enhance our understanding of hair graying. More importantly, discovering this connection will help us understand pigmentation diseases with innate immune system involvement like vitiligo," added co-author William Pavan, chief of the Genetic Disease Research Branch at the National Institutes of Health (NIH).

Vitiligo is a condition that leads to the loss of natural skin color, typically in patches, as cells lose the ability to produce melanin. It affects somewhere between 0.5% to 1% of the human population.